<template>
  <div class="child">
    <h3>我是child组件</h3>
    {{sum}}
  </div>
</template>

<script>
import { ref } from 'vue'
export default {
  name: 'Child',
  setup() {
    let sum = ref(0)
    return new Promise((resolve, reject) => {
      setTimeout(() => {
        resolve({sum})
      },3000)
    })
  }
};
</script>

<style scoped>
  .child {
    background-color:  skyblue;
    padding: 10px;
  }
</style>